Conventionally, it is believed that a blood pressure value is one of the most important indexes on health management, and the management of the blood pressure value is treated as important. Furthermore, recent researches show that a blood pressure measured during nighttime becomes an important index for management of a cardiovascular risk.
From such standpoints, various techniques of measuring the nighttime blood pressure have been disclosed. For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2001-70260) discloses a technique in which, in an electronic blood-pressure meter, a clock time at which the blood pressure is measured is previously set, and the blood pressure is measured at the set clock time.
In addition, Patent Document 2 (Japanese Unexamined Patent Publication No. 8-131408) discloses a technique of measuring the blood pressure as a trigger that the subject becomes in a sleep state. Specifically, in a sleep health management system disclosed in Patent Document 2, a determination whether or not body motion exists is made based on a signal obtained from a vibration sensor attached to bedclothes, the determination that the subject is in the sleep state is made when the body motion is not recognized for a predetermined time, and the blood pressure is measured as the trigger of the determination that the subject is in the sleep state.